Movement discoordination in individuals with spastic hemiparetic cerebral palsy (SH-CP) may be caused by stereotypic multi-joint movement patterns (synergies), reflecting a loss of independent joint control. Specifically in the paretic upper limb, shoulder abduction and elbow/wrist/finger flexion (flexor-synergy) and shoulder adduction/elbow extension (extensor-synergy) could be coupled in individuals with moderate to severe SH-CP. As part of this R01 proposal, we plan to investigate the presence and extent to which discoordination exists in individuals with SH-CP. In an effort to study the possible loss of independent joint control in this population, we propose to determine the presence and the effect of abnormal elbow/shoulder/wrist/hand torque and force coupling under static and dynamic conditions. We intend to identify and quantify: 1) under isometric conditions, the presence of abnormal voluntary torque patterns in the impaired upper limb, 2) under dynamic conditions, the effect of limb loading on 3-D upper extremity active elbow/shoulder range of motion and spontaneous finger flexion forces, and 3) differences in morphology between brain hemispheres and fiber density in individuals with SH-CP and control subjects and its relationship with reductions in work area, increases in finger flexion forces (aim 2) and level of hand impairment. We hypothesize that during the generation of isometric maximum torques, an abnormal torque coupling will be found between the shoulder and elbow in the paretic arm. Furthermore, we expect workspace of the paretic arm to decrease and finger flexion forces to increase for increasing levels of abduction torques and shoulder abduction angles. This will be studied by changing the level of support of the subject's arm and the movement plane over horizontal versus inclined and declined planes generated by a 3-D force controlled robot arm. Finally, we hypothesize that the loss of independent joint control and hand function is correlated with expected changes in brain morphology in individuals with SH-CP. This study will make the first step into the characterization of movement discoordination in individuals with CP as well as its relationship to changes in brain morphology. Results from this study will lead to a better understanding of mechanisms and the effect of neural development and maturation underlying brain-injury induced movement impairment. PUBLIC HEALTH RELEVANCE. The proposed study seeks to quantify the loss of independent joint control in the paretic upper limb of children and young adults with spastic hemiparetic cerebral palsy and correlate these findings with expected changes in brain morphology. Understanding mechanisms underlying the loss of independent joint control in this population represents a crucial step to the development of targeted interventions that will be designed to increase independent joint control and thus improve upper limb function.